CVE-2024-40503 identifies a vulnerability in the Tenda AX12 router firmware version 16.03.49.18_cn+ that allows a remote attacker to cause a denial of service (DoS) condition by exploiting weaknesses in the device's routing functionality and ICMP packet processing. The flaw is categorized under CWE-940, which relates to improper handling of exceptional conditions, leading to resource exhaustion or device crashes. The vulnerability can be triggered remotely without any authentication or user interaction, making it accessible to attackers who can send specially crafted ICMP packets to the affected device. The impact is limited to availability, as the vulnerability does not compromise confidentiality or integrity of data. The CVSS v3.1 base score is 6.5, reflecting a medium severity level with attack vector as adjacent network (AV:A), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), unchanged scope (S:U), no confidentiality or integrity impact (C:N/I:N), and high availability impact (A:H). No patches or fixes have been published at the time of disclosure, and no known exploits have been reported in the wild. This vulnerability could be leveraged to disrupt network operations by causing the router to crash or become unresponsive, potentially affecting business continuity and network reliability for organizations relying on this hardware. The Tenda AX12 is a consumer and small business router, commonly used in Asia and other regions where Tenda has market presence. The vulnerability highlights the importance of robust ICMP and routing protocol handling in network devices to prevent denial of service attacks.

The primary impact of CVE-2024-40503 is a denial of service condition on affected Tenda AX12 routers, which can lead to network outages and loss of connectivity for end users and organizations. This disruption can affect business operations, especially for small businesses or home offices relying on these routers for internet access and internal networking. The vulnerability does not expose sensitive data or allow unauthorized access, so confidentiality and integrity impacts are negligible. However, the availability impact is significant as it can cause device crashes or reboots, leading to downtime. Since the attack requires only network adjacency and no authentication, attackers within the same local network or connected via WAN (if ICMP is not filtered) can exploit this vulnerability. The lack of known exploits in the wild reduces immediate risk, but the absence of patches means the vulnerability remains open to potential future exploitation. Organizations using Tenda AX12 routers should consider the risk of service disruption and plan accordingly to maintain network resilience.

1. Restrict ICMP traffic: Implement firewall rules to limit or block ICMP packets from untrusted sources, especially on WAN interfaces, to reduce exposure to malicious ICMP packets. 2. Network segmentation: Isolate vulnerable devices on separate network segments to limit the attack surface and reduce the risk of lateral movement. 3. Monitor network traffic: Use intrusion detection/prevention systems (IDS/IPS) or network monitoring tools to detect unusual ICMP traffic patterns indicative of exploitation attempts. 4. Vendor engagement: Regularly check for firmware updates or patches from Tenda addressing this vulnerability and apply them promptly once available. 5. Device replacement: For critical environments, consider replacing vulnerable Tenda AX12 routers with devices from vendors with stronger security track records and timely patching. 6. Disable unnecessary routing features: If feasible, disable or limit routing functionalities that are not required to reduce the attack surface related to routing and ICMP handling. 7. Incident response planning: Prepare response procedures to quickly isolate and remediate affected devices in case of exploitation attempts.